1. Technical Field
The presently disclosed subject matter relates to a light emitting device.
2. Description of the Related Art
As shown in FIG. 1, compact liquid-crystal displays for current cellular phones, digital still cameras (DSC), and other similar devices utilize a backlighting source (backlighting unit). As a light source device for these types of devices, an edge emitting LED or side-view package (hereinafter referred to as the side-view package) is utilized, which emits light mainly in parallel with the surface of a mount substrate. The side-view package is placed in front of the light-receiving face of a light guide plate, so that light emitted from the side-view package can be incident on the light-receiving face and guided through the light guide plate. This configuration constitutes a surface emitting backlighting unit which has little or no unevenness in intensity of light.
FIGS. 2 to 4 illustrate a conventional side-view package (light emitting device).
The side-view package shown in FIG. 2 is configured to include a white substrate cup formed by insert molding or the like, a light emitting element placed in the white substrate cup, and a phosphor-containing resin (sealing resin added with phosphor) injected into the cup to encapsulate the light emitting element and hardened. In this instance, the white substrate serves to reflect the light emitted from the light emitting element. The white substrate is generally formed of a molded resin, and specifically, formed of PPA (polyphthalamide), LCP (liquid crystal polymer), nylon, or the like.
FIG. 3 shows a light emitting device disclosed in Japanese Patent Application Laid-Open No. 2004-363503. In order to prevent leakage of light from the white substrate that is formed as shown in FIG. 2, the light emitting device (or a light source body 1) is configured such that a bottom face portion, a top face portion, and a rear face portion of the white substrate (the light source body 1 formed of a molded resin) are covered with an external reflector 10 (i.e., the external reflector 10 is composed of a bottom face portion 11, a top face portion 12, and a rear face portion 13). It should be noted that the reference alphanumeral 1a denotes a light emitting face in FIG. 3.
FIG. 4 shows a light emitting diode chip disclosed in Japanese Patent Application Laid-Open No. 2005-223082. The light emitting diode chip 21 includes: a chip substrate 22; a light emitter (an LED 24) to be mounted on the substrate 22; an optically transparent resin body 25 for encapsulating the LED 24 on the chip substrate 22; a reflective frame body 26; and a thin metallic reflective film 27. The chip substrate 22 is formed of glass epoxy or BT resin (Bismaleimide Triazine Resin) or the like. The reflective frame body 26 includes reflective faces 26a, 26b, and 26c configured on an interior portion for surrounding three sides of the optically transparent resin body 25. The thin metallic reflective film 27 is formed on top of the optically transparent resin body 25 by vapor deposition, plating, transfer or the like. Thus, a certain directivity of light emitted from the LED 24 is provided for a resin face (being a light emitting face 25a) of the optically transparent resin body 25 that is not surrounded by the reflective frame body 26 and the reflective film 27.
In this instance, the chip substrate 22 is provided with an electrode terminal 23 for electrically communicating with the LED 24 and for being bonded to a mount substrate 29. The LED 24 is a very small square chip which has a pair of element electrode portions (being anode and cathode electrodes). The element electrode portions of the LED 24 are connected to the electrodes on the chip substrate 22 by die bonding or wire bonding.
Further, the optically transparent resin body 25 is formed in a cubic shape by a transparent or milk-white like translucent epoxy or silicon-based resin material being filled therein about the LED 24 on the chip substrate 22. The reflective frame body 26 is formed of a resin molded body or a metal molded body so as to surround the three sides of the optically transparent resin body 25 as shown in FIG. 4 just like an angular U-shape. In this instance, the resin molded body is molded of a resin material which contains a highly reflective member material such as titanium oxide or other metal particles, and the metal molded body has a surface which has a reflective coating.
Recently, the light guide plate of backlights has become thinner as cellular phones and digital still cameras are reduced in thickness. Accordingly, the market demands a thinner side-view package for the light source.
However, the light emitting device shown in FIG. 2 is relatively thick because the sealing resin is surrounded with the white substrate and therefore the white substrate is present in the direction of height of the side-view package.
Furthermore, the light emitting device shown in FIG. 3 can prevent the leakage of light from the white substrate. Nevertheless, the bottom face portion and the top face portion of the white substrate are provided with an external reflector, thereby causing the light emitting device to be increased in thickness.
In addition, the light emitting diode chip shown in FIG. 4 has the thin metallic reflective film formed instead of the white substrate in the direction of height of the side-view package, thereby relatively reducing the thickness of the side-view package to a certain extent. However, the presence of the chip substrate (electrode substrate) below the chip imposes a limitation to a further reduction in thickness.
Furthermore, the light emitting diode chip shown in FIG. 4 employs a metallic reflective film serving as the reflective film 27, thereby causing a decrease in luminous flux (luminous flux drop) as described later.